1. Technical Field of the Invention
The present invention relates to an optical disc driving apparatus, and more particularly to an optical disc driving apparatus to be installed in an automotive vehicle to drive an optical disc such as for example a compact disc and a digital versatile disc while reading out information contained in the optical disc.
2. Description of the Related Art
Up until now, there have been provided a wide variety of optical disc driving apparatuses each of which can drive a plurality of optical discs including a digital versatile disc and a compact disc to reproduce information from data recorded in the optical discs. One of the conventional optical disc driving apparatuses is disclosed in, for example, Japanese Patent Laying-Open Publication No. 2001-344861 and shown in FIGS. 15 to 20. The conventional optical disc driving apparatus 300 is herein shown as comprising a housing 310, and a turntable 322 provided at the center of the housing 310. The housing 310 has a front plate and a rear plate, the front plate being formed with a loading slot 311 having two kinds of optical discs different in size, for example, 8-centimeter diameter and 12-centimeter diameter pass therethrough. Herein shown in FIGS. 16 to 20 is an optical disc 390 of 8-centimeter diameter which will be described hereinafter.
The turntable 322 is rotatably supported by the housing 310 to retain and rotate the optical disc 390. The turntable 322 has a center axis around which the turntable 322 is rotated, and the housing 310 has a center plane passing though the center axis of the turntable 322. The conventional optical disc driving apparatus 300 further comprises a guide plate 340 which is positioned within the housing 310 in the vicinity of the loading slot 311 and supported by the housing 310. The guide plate 340 has an inner surface 341 contactable with the optical disc 390 to guide the optical disc 390 toward the turntable 322 until the optical disc 390 is retained by the turntable 322 after being partly passed through the loading slot 311.
The conventional optical disc driving apparatus 300 further comprises a rotation shaft 352 having a center axis perpendicular to the center plane of the housing 310, and supported by the housing 310 with the center axis being in parallel relationship with the inner surface 341 of the guide plate 340 along the center plane of the housing 310, viz., when seen from the front plate of the housing 310. The rotation shaft 352 has an intermediate plane on the center plane of the housing 310, and two different longitudinal portions including first and second side portions 353 and 354 integrally formed with each other at the intermediate plane and tapered toward the intermediate plane. The left and right positioning pins 370a and 370b are adapted to position the optical disc 390 while the optical disc 390 is loaded on the turntable 322. The left and right positioning pins 370a and 370b are fixedly mounted on the housing 310 in the vicinity of the rear plate of the housing 310 and in spaced relationship with each other across the center plane of the housing 310. The conventional optical disc driving apparatus 300 further comprises driving means for driving said rotation shaft 352. The following description is directed to the operation of the conventional optical disc driving apparatus 300 in which the optical disc 390 of the 8-centimeter diameter is driven to rotate by the turntable 322.
Firstly, the optical disc 390 is loaded through the loading slot 311 formed in the housing 310. The lateral length of the loading slot 311 is larger than the diameter of the optical disc 390. It is, here, assumed that the optical disc 390 is inserted through the left end portion 311a of the loading slot 311 by an operator as seen in FIG. 17. At this time, the left peripheral surface of the optical disc 390 is positioned in neighborhood of the left end portion 311a of the loading slot 311, while the left lower peripheral surface is brought into contact with the first side portion 353 of the rotation shaft 352. Under these conditions, the optical disc 390 is subject to a driving force compounded by first and second directional forces in the directions shown respectively by arrows 301 and 303 both of which are caused by the rotation of the rotation shaft 352 under the influence of the friction force generated in a contact area between the optical disc 390 and the first side portion 353 of the rotation shaft 352. This results in the fact that the optical disc 390 is rotated in a rotation direction shown by an arrow 302 in FIG. 19 and conveyed in the direction 303 by the first and second directional forces respectively in the directions 301 and 303. The first directional force of the driving force in the direction 301 is caused by the rotation of the rotation shaft 352, while the second directional force of the driving force in the direction 303 is caused by the tapered first side portion of the rotation shaft 352. Here, the contact area is shown in FIG. 18 by a block of crossed lines as at 330. The optical disc 390 is then conveyed toward the turntable 322 until the outer peripheral surface of the optical disc 390 is brought into engagement with the left positioning pin 370a in FIG. 19. When the outer peripheral surface of the optical disc 390 is brought into engagement with the left positioning pin 370a, the right lower peripheral surface of the optical disc 390 is in turn brought into contact with the second side portion 354 of the rotation shaft 352. At this time, the optical disc 390 is subject to a driving force compounded by first and second directional forces in the directions 301 and 303 and a third directional force in a direction opposite to the direction 303. The first directional force in the direction 301 caused by the rotated first side portion 353 is larger than the first directional force in the direction 301 caused by the rotated second side portion 354, while the second directional force in the direction 303 caused by the rotated first side portion 353 is also larger than the third directional force in the direction opposite to the direction 303 caused by the rotated second side portion 354. This means that the second directional force in the direction 303 caused by the rotated first side portion 353 is reduced by the third directional force in the direction opposite to the direction 303 caused by the rotated second side portion 354. The rotation force in the rotation direction 302 is reduced by the first directional force in the direction 301 caused by the rotated second side portion 354.
The optical disc driving apparatus 300 thus constructed as previously mentioned, however, encounters such a problem that the optical disc 390 frequently fails to be retained by the turntable 322 without being in axial alignment with the turntable 322. Additionally, the optical disc driving apparatus 300 tends to need a relatively long time for the optical disc 390 to be retained by the turntable 322.